Endocrine and Behavioural Responses of Male Greylag Geese (Anser anser) to Pairbond Challenges during the Reproductive Season

Authors

  • Katharina Hirschenhauser,

    1. Konrad Lorenz Forschungsstelle für Ethologie, University of Vienna, Institute of Biochemistry and Ludwig Boltzmann Institute of Veterinarian Endocrinology, Veterinary University Vienna, and Institute of Zoology, University of Vienna, Vienna
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  • Erich Möstl,

    1. Konrad Lorenz Forschungsstelle für Ethologie, University of Vienna, Institute of Biochemistry and Ludwig Boltzmann Institute of Veterinarian Endocrinology, Veterinary University Vienna, and Institute of Zoology, University of Vienna, Vienna
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  • Bernard Wallner,

    1. Konrad Lorenz Forschungsstelle für Ethologie, University of Vienna, Institute of Biochemistry and Ludwig Boltzmann Institute of Veterinarian Endocrinology, Veterinary University Vienna, and Institute of Zoology, University of Vienna, Vienna
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  • John Dittami,

    1. Konrad Lorenz Forschungsstelle für Ethologie, University of Vienna, Institute of Biochemistry and Ludwig Boltzmann Institute of Veterinarian Endocrinology, Veterinary University Vienna, and Institute of Zoology, University of Vienna, Vienna
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  • Kurt Kotrschal

    1. Konrad Lorenz Forschungsstelle für Ethologie, University of Vienna, Institute of Biochemistry and Ludwig Boltzmann Institute of Veterinarian Endocrinology, Veterinary University Vienna, and Institute of Zoology, University of Vienna, Vienna
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Corresponding author: Katharina Hirschenhauser, Institute of Zoology, University of Vienna, Althanstr. 14, A 1090 Vienna, Austria. E-mail: k.hirschenhauser@aon.at

Abstract

Although greylag geese Anser anser establish long-term monogamous pairbonds, some of the existing pairs do split up (divorce) and new pairs are formed during the annual spring mating period. In this study, male greylag geese which were involved in the challenge of an existing pairbond (challenged males and challengers) were regarded as ‘natural experimental’ groups and compared with males in stable pairbonds (unchallenged males and male-paired males, a common male strategy when the availability of females is low). In total, 37 males were investigated. The analysis included a description of the seasonal patterns of hormone levels, aggression and courtship. We tested whether hormone levels correlated with aggressive and courtship behaviours. Finally, we compared hormonal and behavioural patterns amongst the four groups. Immunoreactive testosterone (T) and corticosterone (B) equivalents were measured in faecal samples. Individual hormone levels were correlated with frequencies of agonistic male-male interactions and with frequencies of male-female courtship. During early mating and pre-laying phases, T was at its seasonal maximum, which may have masked hormone-behaviour correlations. During egg-laying, at the onset of seasonally decreased T, agonistic male-male interactions and the frequencies of courtship behaviour were significantly correlated with T. Unchallenged males had higher rates of agonistic interactions than any other males. However, unchallenged and challenged males tended to excrete T at higher levels than challengers. The high rates of being attacked and elevated levels of faecal B were indicative of the social conflict experienced by challengers. No hormonal differences were observed between heterosexually paired males and male-paired males. In summary, pairbond status and situations of social conflict had a modulating effect on T and B; however, in this study, the two hormones seem to be affected independently of one another.

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